A common method of treatment used in restoring blood flow through a diseased segment of a blood vessel is balloon angioplasty. This treatment generally involves the use of a balloon catheter. The balloon catheter is introduced into the cardiovascular system of a patient through an artery, such as the brachial or femoral artery, and is advanced through the vasculature until the balloon attached to the distal end of the catheter reaches the diseased vessel. The balloon is placed across the diseased vessel segment and is inflated with sufficient pressure to cause the deposit on the intravascular surface to compress against the vessel wall. The balloon is then deflated to a small profile so that the balloon catheter may be withdrawn from the patient's vasculature and the blood flow resumes through the dilated artery.
Angioplasty of an artery to correct flow obstruction in the vessel may stimulate excess tissue proliferation which then blocks (through restenosis) the newly reopened vessel, precipitating a need to perform a second angioplasty procedure. Alternatively, a more drastic procedure such as a surgical bypass operation may be required to repair or strengthen the vessel. To reduce the likelihood of restenosis and to strengthen the diseased vessel segment, an intravascular intraluminal prosthesis may be implanted within the segment of the diseased vessel to maintain vascular patency.
Intraluminal prostheses are tubular structures, such as a stent, graft, patch, or the like, which are radially expandable to hold a narrowed blood vessel in an open configuration. While intraluminal prostheses are most often used to hold blood vessels open, intraluminal prostheses can also be used to reinforce collapsed or narrowed tubular structures in the respiratory system, the reproductive system, biliary ducts or any other tubular body structure. The intraluminal prosthesis is typically transported through the patient's vasculature in a small, compressed delivery configuration, and then is enlarged to a larger, expanded configuration at the implantation site. The expansion is often accomplished by inflation of a balloon portion of the catheter contained within the compressed intraluminal prosthesis, but self-expanding intraluminal prostheses made from a memory alloy or spring-like structure may be used, with or without a balloon assist.
Since the catheter and intraluminal prosthesis will be traveling through the patient's vasculature, the intraluminal prosthesis must be compressed to a small delivery diameter and must be firmly attached to the catheter before insertion into the body. Thus, the intraluminal prosthesis must be positioned on the catheter so as not to interfere with delivery, and the intraluminal prosthesis must not slip off the catheter before it reaches the desired location for deployment.
In conventional procedures, it is necessary to crimp the intraluminal prosthesis onto the catheter, optionally with a balloon inside the intraluminal prosthesis, to reduce the intraluminal prosthesis's diameter and to prevent it from sliding off the catheter while the catheter is advanced through a patient's vasculature. Non-uniform crimping can result in relatively sharp edges being formed along the uneven surface of the compressed intraluminal prosthesis. In addition, non-uniform intraluminal prosthesis compression may result in an intraluminal prosthesis/catheter profile that is larger than necessary. Where the intraluminal prosthesis is not reliably compressed onto the catheter, the intraluminal prosthesis may slide off the catheter and into the patient's vasculature prematurely, which may cause thrombosis. Thus, it is important to ensure the proper compression of an intraluminal prosthesis onto a catheter in a uniform and reliable manner.
Manual crimping of the intraluminal prosthesis tends to result in uneven compression due to uneven application of force. Furthermore, it is difficult to determine when a uniform and reliable compression has been achieved by hand. In addition, due to the flexible nature of the intraluminal prosthesis, some self-expanding intraluminal prostheses are difficult to load by hand into a balloon catheter. Minimizing direct human manipulation may decrease the likelihood of human error, and increase the consistency of the compression procedure. Hence, there is a need for a device for reliably and uniformly compressing an intraluminal prosthesis onto a catheter.
There are several known mechanisms devised for loading an intraluminal prosthesis onto a catheter. For example, U.S. Pat. No. 5,911,452 shows a chamber with a flexible tubular diaphragm into which a deflated balloon catheter can be inserted with the intraluminal prosthesis. The chamber is then pressurized to crimp the intraluminal prosthesis onto the deflated catheter balloon. U.S. Pat. No. 6,009,614 shows another intraluminal prosthesis crimping chamber utilizing fluid pressure to crimp the intraluminal prosthesis onto a deflated catheter balloon. U.S. Pat. No. 5,810,838 shows further examples of pressurized chambers and collapsible tubular sleeves for compressing intraluminal prostheses onto balloon catheters. U.S. Pat. No. 5,971,992 shows yet another example of a pressurized chamber. U.S. Pat. No. 5,746,764 shows further devices for compressing intraluminal prosthesis onto balloon catheters that include both vacuum and pressurizing fluid pressure means for compression of the intraluminal prosthesis onto the catheter balloon. U.S. Pat. No. 5,944,735 shows yet another example of the intraluminal prosthesis compression device. U.S. Pat. No. 5,972,028 shows another variation of an intraluminal prosthesis compression device. U.S. Pat. No. 5,860,966 shows another version of an intraluminal prosthesis compression apparatus employing a pressurized diaphragm to compress the intraluminal prosthesis. Finally, U.S. Pat. No. 6,745,445 shows inflating an angioplasty balloon inside a vascular intraluminal prosthesis in order to secure the vascular intraluminal prosthesis upon the balloon and applying uniform compression pressure around the balloon/intraluminal prosthesis unit. The pressure chambers of these various patents require time-consuming and expensive calibration and maintenance in order to assure uniform and complete compression of the intraluminal prostheses. A method that enhances uniform distribution of the compression pressure and/or reduces the necessary calibration and maintenance would allow more even distribution of pressure during the intraluminal prosthesis compression process.
In addition, it is desirable to hold the intraluminal prosthesis in a compressed position inside the catheter for installation in the patient and possibly for an extended storage period. Particularly in the case of a self-expanding intraluminal prosthesis, it may be difficult for a user to prevent a compressed intraluminal prosthesis from expanding upon removal from one of the above pressure chambers.
Lined intraluminal prostheses, which have a layer of synthetic or biological material covering at least part of an inner or outer surface of the intraluminal prosthesis, are becoming more prevalent as technologies arise to facilitate provision and use of such lined intraluminal prostheses in an economical and efficient manner. These lined intraluminal prostheses present particular challenges to achieving compression and storage as desired. Lined intraluminal prostheses have an increased wall thickness as compared to unlined intraluminal prostheses, and this extra bulk may necessitate higher pressure to compress the lined intraluminal prosthesis than might be required by an unlined intraluminal prosthesis. Care must also be taken that structures of the intraluminal prosthesis do not wear away or puncture the relatively delicate lining during the compression process, particularly under the increased compression forces needed for the lined intraluminal prosthesis. Additional considerations arise when the lining is biological, as natural tissue linings must be kept hydrated to avoid cracking and breakage.
Accordingly, it is desirable to provide a method and apparatus of compressing intraluminal prostheses which economically and efficiently provides even compression pressure, allows for ease in transporting and storing a compressed intraluminal prosthesis, and avoids mechanical or dehydration damage to a lined intraluminal prosthesis.